Electric heating unit



Oct. 2, 1928.

J. C. WOODSON ELECTRIC HEATING um:

Filed April 24, 1925 2 Sheets-Sheet INVENTOR James C- M W TORNEY QR. 12m? Oct. 2,. 1928.

J. C. WOODSON ELECTRIC HEATING UNIT Filed April 24, 1925 2 Sheets-Sheet 2 llllllilll INVENTOR Jbmes C. l/x oodson WITNESSES: 33%

w TTORNEY Patented Oct. 2, 1928.

- N TED STATES PATENT OFFICE.

JAMES C. WOODSON, OF-EAST IPITTSBURGI-I, PENNSYLVANIA, ASSIGNOR TO WESTING- HOUSE ELEC'IRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYL- VAN IA.

, ELECTRIC HEATING imr'n,

'Applicationfiled April 24, 1925, Serial No. 25,606.

My invention relates to electric heating devices and particularly to electric heating units. p

' One object of my invention is toprovide a 6 relatively simple and efficient heating unit having means for preventing accidental grounding of the resistor to a supporting means.

practicing my invention, I provide a plurality of refractory members, ofelectricinsulatin material, havinggrooves in one surface thereof, supported'inabutting and overlapping relation by an interfitting means. I

Inthe drawings,

heating unit embodying my invention,

. Fig. 2 is a view n side elevation thereof,

Fig. 3 is a view in end elevation thereof, Fig. 4 is a view in lateral section there through, taken on the line IVIV of Fig. 1, I Fig. 5 is a view, in lateral section, through a modified form of device embodying my invention, and I i r Fig. 6 is a view in lateral section through a still further modification of a device embodying my invention.

A heating unit designated generally by the numeral 11 comprises a metal member 12, of substantially overhung channel section and of sheetmetal of proper thickness in order that itmay have suflicient strength to support refractory members to belocated therein.

located in the member 12 in overhanging end-to-end relation. One end of each of the members 13 is provided with an upper overhung portion, designated by 14 and the other end thereof is provided with a lower projecting portion 15, substantially as illustrated in Fig. 2 of the drawings. The projecting portion 15 is provided with a groove 16 in the upper surface thereof that extends laterally of the assembled heating unit 11.

, Each of the members 13 is provided with a plurality of undercut grooves 1'? in the upper surface, that extend longitudlnally of the heating unit and are located in spaced and alined relation to receive a resistor member 18 that is constituted by a wire wound to open helical form. At one end of the heating unit 11 there is provlded an end member 19, of ceramic electriednsulating Figure 1 is a topplan view of an electric thereon b5 A plurality of refractorymemberslii are material, having its upper surface partially grooved in the same manner as are the mem bers 13 and having also an arcuate open groove 21 connecting the inner ends of each pair of adjacentgrooves 17, substantially as illustrated in Fig. 1 of the drawing.

"At the other end of the heating unit, I

provide a terminal assembly comprising a bottom refractory member 22 having an end shoulder portion 23 and a groove 16 therein, the same as the members 13. I provide also an upper refractory member 24 that has a plurality of spaced openings 25 extending vertically therethrough. A plurality of ter- 'mlnal memers 26 are located in the respective openings 25 and comprise short machine screws or bolts, the heads of which are located in enlarged end portions 27 of the openings 25. The ends of the resistor member '18 are connected to the bolts 26 and held co-operating nuts 28.

I provi e three such terminal members and make the connections such that the two portions of the resistor member 18 may be connected in series-circuit relation or in parallel-circuit relation relatively to each other or that the portions may be energized singly, in a manner well known in the art.

1 It is to be noted that the members 13 and the member 19 are severally provided with laterally extending integral portions 29 and 31 which fit into the members 12 of overhung channel section. The grooves 17 are located in the upper portion of the members 13 and 19 and the walls thereof, particularly the end walls indicated. by the numerals 32 and 33, are made relatively high in order that the creeping distance between'the resistor located in the bottom portion of the groove 17 and the highest part of the metal member 12 may be as large as possible in order to prevent a ground occurring when a heating unit is located for a long time in a dusty place and perhaps in an inaccessible place, where it can not be easily cleaned. This is particularly the case, when heatingunits of this kind are used in street car heaters, and the device embodying my invention has been developed particularly for such application.

I have illustrated a modified form of device embodying my invention in Fig. 5 of the drawing, wherein a metal member 34, of

is employed to maintain a plurality of ceramic members 35 in proper overhung and cnd-to-end alinement. The members 35 are provided with undercut grooves 36, of substantially the same character as the grooves l? and are also provided with the co0perating shoulder portions hereinbefore described in connection with the members 13. It. may be noted that the distance between a resistor member located within an end groove 36 and.

the metal supporting member Set is relatively much greater in the modification illustrated in Fig. 5, than in that illustrated in Fig. 4:.

Fig. 6 illustrates a still further modification in which a plurality of refractory members 37. of electric-insulating material and of substantially the sameform in lateral seotion as the member 13 are located in abutting and overhanging relation, as was hereinbefore described for the members 13. The members 37 are provided with lateral integral portions at each side thereof and openings 89 are located therein to receive rod members 4:1. extending therethrough, which are provided in place of the metal members of substantially channel form hereinbefore described. The members 3'7 are otherwise of substantially the same shape at the. end portions thereof as was hereinbefore described for the members 13 in that they are provided with upper and lower integral shoulder portions which overlap when the members are assembled in proper operative positions relatively to each other.

I have hereinbefore described the length of the creeping distance between the resistor member located in the overhung grooves and the metal support at the sides or edges of the respective refractory supporting members. If each of the members 13, for instance, were made without the shoulder portion, the creeping distance from a resistor member to the metal support, between the abutting members 13, would be simply that of a straight line connecting the two portions. If the heating unit were installed in a dusty place or in a. place where it was subject to deposits of metallic particles, it possible that the resistor member would soon be grounded by the dust of metallic particles sifting down between the adjacent ends of the members. By providing upper and lower shoulder portions, as was hercinbeitore described, and as is more particularly illustrated in Fig". 2 of the drawings, I am able to increase this creeping distance in accordance with the amount ot overhringing or overlapping of the adjacent refractory members.

The grooves 16 provide means for receiving and holding a certain amount of dust or of. metallic particles that may sift down between the adjacent ends of the members 13 or between the members 13 and the end members, whereby it is possible to maintain that portion of the crevice between two abutting members just above the metal supportinq member 12 substantially freefrom dust tor a relatively long period of time. This provision effectively prevents grounding except under very severe conditions.

Various modifications and changes may be made without departing from the spirit and scope of the appended claim, and I desire that all such modifications shall be included.

I claim as'my invention:

In an electric heater, in combination, a plurality of grooved refractory electric-in sulating members located in abutting relation and having their adjacent edge portions overlapping each other, metal supporting means for said refractory members inter-litting therewith, a refractory terminal-member-supporting plate at one end of said heater, and a refractory spacing plate between said tcrminal-lnember-supporting plate and said metallic supporting means.

In testimony whereof, I have hereunto subscribed my name this 20th day of April,

J. C. XVOOD'SON. 

